Bring a large pot of salted water to a boil and cook the rigatoni according to package directions until al dente. Drain and keep warm.
While the pasta cooks, heat the olive oil in a large sauté pan over medium heat.
Season the cubed chicken thighs with kosher salt and black pepper, then add to the hot pan and cook until cooked through and browned, about 3–4 minutes per side.
Add the minced garlic to the pan with the chicken and cook for 1 minute, stirring, until fragrant.
Add the cream cheese to the pan and stir until it melts and forms a smooth base for the sauce.
Stir in the peas, marinara sauce, and shredded Parmesan; simmer gently until the cheese is melted and the sauce is smooth.
Pour in the heavy cream, stir to combine, bring back to a low simmer for a minute to heat through, then remove the pan from the heat.
Toss the drained rigatoni into the sauce until evenly coated, then serve topped with additional Parmesan and chopped fresh basil if desired.